Preparation of vinyl halides



Patented Dec. 9, 1941 PREPARATION OF HALIDES Archie B..Japs, CuyahogaFalls, Ohio, assignor to The B. F. Goodrich Company, New York, N. Y., acorporation of New York No Drawing. Original application July 19, 1938,

Serial No. 220,129. Divided and this application February 14, 1940,Serial No. 318,886

7 Claims.

This invention relates to the preparation of vinyl halides by theaddition of a hydrogen halide to acetylene, and has as its principalobject to provide a catalyst having longer life and greater activitythan catalysts now known.

It is known that when a gaseous mixture 'of hydrogen chloride andacetylene is passed over mercuric chloride at an elevated temperaturevinyl chloride is formed. These vapor phase reactions are ordinarilycarried on at from 180 to 250 C., and are strongly exothermic. Mercuricchloride, however, has a vapor pressure of 25 mm.

of mercury at 200 C., of '75 mm. at 225 C., of

over 150 mm. at 250 0., and of760 mm. at 301 C. It can be readily seenthat whenever mercuric chloride is used as the catalyst in a vapor phasereaction, not only is the catalyst :quickly lost by sublimation, but acontaminated product is produced. This fundamental difliculty withmercuric chloride has led to the search for other catalysts, but nomaterial as active as mercuric chloride has previously been discovered.-Less active materials have often been used, however, in spite of the lowyields obtained, to enable the reaction to be performed in the optimumtemperature range.

I have discovered that complex salts of mer-. curic chloride andchlorides of alkaline earth metals are catalysts for the addition ofhydrogen chloride to acetylene. Not only are these materials much lessvolatile than mercuric chloride, but they give increased conversion tovinyl chloride.

Any complex salts within the class defined may be profitably employed ascatalysts. Double salts such as HgCh-CaClz and HgClz-BaCla are verysatisfactory materials. Other complex salts such as HgClz-2BaClz,HgCli-ZSrCla, and

HgClz CaClz BaCl-z may also be used if desired. Since magnesium chlorideis similar in many of its properties to the alkaline earth chlorides, itis considered for the purposes of this invention to be the equivalentthereof and is included within the scope-of the claims. The particularcomplex salt employed will naturally depend upon the temperature atwhich the reaction is being performed, complex salts containing higherproportions of the alkaline earth metal chlorides being employed athigher temperatures.

etc, are ordinarily employed, although other materials having highsurface action, of which a number are now known, maybe used if desired.

The complex salts may be formed in any desired manner. Although mercuricchloride is only slightly soluble in cold water, mixtures of mercuricchloride and an alkaline earth metal chloride dissolve readily. In apreferred method of preparing the catalyst, acetone or otherpenetration-assisting material is added to an aqueous solution of thecomplex salt, and the solution is absorbed on activated charcoal. Theimpregnated material is then dried in an oven, as much of the. water aspossible being removed because the anhydrous complex salts catalyze thereaction to a much greater extent'than the materials containing evensmall amounts of water.

The extent of the improvement eifected by this invention is illustratedby the following comparative tests. Equimolar quantities of acetylenefrom which phosphine, ammonia, and hydrogen sulfide had been removed andanhydrous hydrogen chloride were passed at about 200 C. through a tubecontaining a catalyst consisting of .33 gms. of mercuric chloridedeposited upon 127 grams of activated charcoal. In another test, acatalyst consisting of a complex salt containing mercuric chloride 33grams and barium chloride 30 grams deposited upon 12? grams of activatedcharcoal was substituted for the mercuric chloride catalyst. Since thecatalytic action under the above conditions is essentially a local one,the rate of deterioration of the catalyst could be determined bymeasuring the rate of movement of the exothermic reaction zone along thetube. In this test it was found that 25% of the mercuric chloridecatalyst had deteriorated in 80 minutes, while the complex salt ofmercuric chloride and barium chloride was used for 230 minutes before25% of the catalyst was exhausted. In addition, the complex saltcatalysts gave nearly quantitative conversions whereas only 65% of thetheoretical conversion was obtained with the mercuric chloride.

The percent conversion obtained when a carrier of high surface action isused is dependent to a large extent upon the concentration of the doublesalt that is used. Since the reaction is so strongly exothermic, it hassometimes been found advisable to employ two or more catalytic tubes,

the first containing a low concentration of a surface action to causepartial reaction and the other tubes containing successively higherconcentrations oi the complex salt catalyst to complete the reaction. 1

Although this reaction has been described in detail in respect to vinylchloride, it is to be understood that the other vinyl halides may belikewise prepared. vinyl bromide, for instance, may be prepared byreacting acetylene and hydrogen bromide in the presence of a complexsalt of mercuric bromide and an alkaline earth metal bromide. Manymodifications which will be apparent to those skilled in the art areaccordingly within the spirit and scope of theinvention, as defined inthe appended claims.

'llhis application is a division of Serial No. 220,129 filed July 19,1938 now Patent No. 2,225,-

Iclaim:

1. The method of preparing a vinyl halide which comprises reactingacetylene and a hydrogen halide in the vapor phase in the presence of asolid complex salt of a mercuric halide and an alkaline earth metalhalide.

2. The method of preparing vinyl chloride which comprises reactingacetylene and hydrogen chloride in the vapor phase in the presence of asolid complex salt of mercuric chloride and an alkaline earth metalchloride. 3. The method of preparing vinyl chloride which comprisesreacting acetylene and hydrogen chloride in the vapor phase. in thepresence of a solid complex salt of mercuric chloride and an alkalineearth metal chloride, said complex salt being deposited upon a bodyhavinga high surface action.

4. The method 0! preparing vinyl chloride which comprises reactingacetylene and hydrogen chloride in the vapor phase in the presence orasolid double salt or mercuric chloride and barium chloride, said doublesalt being deposited uponactivated charcoal.

5. The method of preparing vinyl chloride which comprises passinganequimolar mixture of acetylene and hydrogen chloride successivelythrough at least two tubes containing a catalyst consisting of a solidcomplex salt ofmercuric chloride and an alkaline earth metal chloride,said complex salt being deposited upon a body having high surfaceaction, the catalyst in the v first tube being present in aconcentration insufilcient to cause complete reaction and the catalystsin the succeeding tubes being present in successively higherconcentrations whereby essentially quantitative conversion is obtained.

.6. A catalyst for the vapor phase reaction or acetylene and a hydrogenhalide to form avinyl

